Update - With Bud's help we did find the relay switch!! DH decided to try another local mechanic and he can work on the MH! Hurray only a few blocks from our house. So it goes in tomorrow and they will change the fuel filter (which should be done after 17 years -right!) and then will do a pressure test.
He personally doesn't think it is anything to do with fuel system - because once it starts (which it has started right up every time DH has tried it since I posted) it runs fine. So anyway they will check it out tomorrow - really thanks for the help because it really was helpful. We have put the elemination process in sequence!!!!